OVERVIEW OF B1 DEFICIENCY

  • Vitamin B1 (thiamine) is water-soluble, comprised of a pyrimidine and a thiazole ring.
  • Dietary sources: Whole-grain cereals, whole-wheat bread, brown rice, legumes, yeast, fresh meats (especially pork).
  • Stability: Destroyed by high temperature and alkaline pH (cooking/baking/pasteurization can reduce bioactivity).
  • Absorption: Occurs in the jejunum and ileum; once in blood, thiamine binds albumin and enters cells by passive diffusion + active transport.
  • Tissue distribution: Heart, skeletal muscle, brain, liver, kidney.
  • Half-life & storage: Biologic half-life 10–20 days; no large tissue depot → continuous dietary intake required.

BIOCHEMICAL ROLE

  • Cofactor for enzymes in carbohydrate and amino acid metabolism:
    • Converts pyruvate to acetyl coenzyme A.
    • Functions in the pentose phosphate pathway.
  • Essential for normal nerve conduction.

BERIBERI

  • Cause: Nutritional deficiency in thiamine.
  • Populations:
  • Clinical features:
    1. Infantile beriberi (by ~2 months):
      • CNS issues: vomiting, nystagmus, purposeless movements, seizures.
      • Cardiac disease: cardiomegaly, tachycardia, cyanosis.
      • Sudden death if untreated.
    2. Adult beriberi:
      • Dry beriberi:
        • Predominantly neurologic.
        • Symmetric peripheral neuropathy (distal paresthesias), muscle weakness (foot/wrist drop), muscle wasting, possible aphonia, emaciation.
      • Wet beriberi:
        • Predominantly cardiac.
        • Cardiomegaly, congestive heart failure signs (dyspnea, orthopnea, edema, tachycardia).
  • Treatment:
    • Supportive care + thiamine supplementation:
      • IV or IM: 50–100 mg daily for ~2 weeks.
      • Then oral dose: ~10 mg/day until full recovery.
    • Evaluate for coexisting vitamin deficiencies.

WERNICKE-KORSAKOFF SYNDROME

  • Most severe thiamine deficiency in adults.
  • Wernicke encephalopathy:
    • Ophthalmoplegia (6th cranial nerve palsy), nystagmus, ataxia, confusion → may progress to coma.
    • Commonly in alcoholics (poor thiamine intake + depletion).
    • Requires urgent treatment: 50 mg IV thiamine daily, then oral.
  • Korsakoff syndrome:
    • Chronic phase after Wernicke encephalopathy.
    • Marked by impaired short-term memory, confabulation.

DIAGNOSIS

  • Blood thiamine measurement:
    • Reference range: 80–150 nmol/L.
    • Levels <80 nmol/L suggest deficiency.

PREVENTION

  • Recommended dietary allowance (RDA) for thiamine:
    • Men: 1.2 mg/day
    • Women: 1.0 mg/day (1.4 mg in pregnancy/lactation)
  • Easy to obtain from a nutritionally balanced diet rich in:
    • Whole grains
    • Legumes
    • Yeast
    • Fresh meats

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